Percentile Rank

In a normal distribution with mean 30 and variance 25, at what percentile rank does a score of 42 fall?

Among twenty-five articles, nine are defective, six having only minor defects and three having major defects.   Determine  the  probability that  an  article  selected at random has major defects given that it has defects.

In a normal distribution with mean 3 and variance 49, what are the upper and lower limit scores for the middle 50% of the data?